The Rt values almost certainly remain above 1 in all regions except London, where the probability that Rt is above 1 is 67%. This indicates that the number of new infections occurring each day will continue to rise, unless further interventions or behavioural changes are introduced.
Despite this, the plots of Rt over time show decreases over the last few weeks in most regions, while showing a plateauing in the South East, South West and East of England. This, together with the Rt remaining greater than 1, means that the number of new infections continues to rise, but at a slower speed.
These lower values of Rt might be the result of the various social distancing interventions, but it is unclear what the impact of any single intervention is from this analysis; and the continued rise in the number of new infections will probably continue unless further interventions or behavioural changes are introduced.
Real-time tracking of an epidemic, as data accumulate over time, is an essential component of a public health response to a new outbreak. A team of statistical modellers at the MRC Biostatistics Unit (BSU), University of Cambridge, are working to provide regular now-casts and forecasts of COVID-19 infections and deaths. This information feeds directly to the SAGE sub-group, Scientific Pandemic Influenza sub-group on Modelling (SPI-M), and to regional Public Health England (PHE) teams.
We fit a transmission model (Birrell et al. 2020) to a number of data sources (see ‘Data Sources’), to reconstruct the number of new COVID-19 infections over time in different age groups and NHS regions, estimate a measure of ongoing transmission and predict the number of new COVID-19 deaths.
We use:
Data are stratified into eight age groups: <1, 1-4, 5-14, 15-24, 25-44, 45-64, 65-74, 75+, and the NHS England regions (North East and Yorkshire, North West, Midlands, East of England, London, South East, South West).
Value of \(R_t\), the average number of secondary infections due to a typical infection today.
The percentage of a given group that has been infected.
NB: negative growth rates are rates of decline. Values are daily changes.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 0.04 | 0.03 | 0.05 |
| East of England | 0.06 | 0.01 | 0.10 |
| London | 0.01 | -0.03 | 0.05 |
| Midlands | 0.05 | 0.02 | 0.07 |
| North East and Yorkshire | 0.04 | 0.02 | 0.06 |
| North West | 0.02 | 0.01 | 0.04 |
| South East | 0.04 | 0.00 | 0.08 |
| South West | 0.08 | 0.03 | 0.12 |
Halving times in days, if a region shows growth than value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | NA | NA | NA |
| East of England | NA | NA | NA |
| London | NA | 20.24 | NA |
| Midlands | NA | NA | NA |
| North East and Yorkshire | NA | NA | NA |
| North West | NA | NA | NA |
| South East | NA | 333.16 | NA |
| South West | NA | NA | NA |
Doubling times in days, if a region shows decline then the value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 16.82 | 12.80 | 24.34 |
| East of England | 12.18 | 7.26 | 48.51 |
| London | 79.54 | 14.66 | NA |
| Midlands | 15.15 | 9.65 | 44.04 |
| North East and Yorkshire | 17.07 | 11.33 | 38.71 |
| North West | 28.08 | 15.99 | 137.04 |
| South East | 15.80 | 8.27 | NA |
| South West | 9.13 | 5.69 | 27.44 |
NB: negative growth rates are rates of decline. Values are daily changes.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 0.05 | 0.04 | 0.06 |
| East of England | 0.06 | 0.02 | 0.10 |
| London | 0.01 | -0.02 | 0.05 |
| Midlands | 0.05 | 0.02 | 0.08 |
| North East and Yorkshire | 0.05 | 0.03 | 0.07 |
| North West | 0.04 | 0.02 | 0.06 |
| South East | 0.05 | 0.01 | 0.09 |
| South West | 0.08 | 0.03 | 0.13 |
Halving times in days, if a region shows growth than value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | NA | NA | NA |
| East of England | NA | NA | NA |
| London | NA | 35.66 | NA |
| Midlands | NA | NA | NA |
| North East and Yorkshire | NA | NA | NA |
| North West | NA | NA | NA |
| South East | NA | NA | NA |
| South West | NA | NA | NA |
Doubling times in days, if a region shows decline then the value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 14.27 | 11.51 | 18.87 |
| East of England | 11.42 | 6.92 | 33.72 |
| London | 47.15 | 13.56 | NA |
| Midlands | 13.62 | 8.91 | 30.19 |
| North East and Yorkshire | 13.77 | 9.62 | 24.76 |
| North West | 17.22 | 11.44 | 33.24 |
| South East | 15.02 | 8.08 | 121.23 |
| South West | 8.89 | 5.54 | 23.96 |
The blue lines is show when interventions have been introduced (lockdown on 23 Mar and the relaxation of measures on 11 May), and the red line shows the date these results were produced (25 Oct).
The figure below shows the probability that \(R_t\) is greater than 1 (ie: the number of infections is growing) in each region over time. Clicking the regions in the legend allows lines to be added or removed from the figure.
Copyright © MRC Biostatistics Unit, University of Cambridge